Blood drop generation devices commonly known as lancets, which are utilized in obtaining blood samples used in performing various blood tests, are well known in the art. These devices operate by creating a small puncture or incision in the patient's skin. Typically, these punctures or incisions are made in the patient's fingertip, although the puncture or incision can be made in other areas of the body such as the foot, arm, or leg.
Prior art lancet devices typically employ a spring loaded cutting blade enclosed within a casing or housing. The person drawing the blood places the housing against the patient's skin and releases the blade with some type of triggering mechanism associated with the device. The potential energy stored within the spring bias of the blade causes the blade to exit the housing and create a puncture or incision in the patient's skin. Accordingly, prior art lancet devices have many advantages including uniform incisions, which can be controlled in terms of location, depth, and sterility. Moreover, because these devices conceal the blade within a housing, the patient is unable to view the often unsettling scene of his or her skin actually being cut. Additionally, many prior art devices include means for retracting the blade back into the housing after the puncture or incision has been made. This feature substantially reduces the danger of spreading disease through contact with the blade. This is an important consideration considering the fact that diseases such as the AIDS virus can be contacted from exposed used blades.
Looking through prior art lancet devices one will discover many different designs which have been developed over the years. The most recent of these designs have retractable blades and other operations that prevent the reuse of the device after a single puncture or incision has been made.
Most prior art lancet devices employ a plunge-type cutting action where the cutting blade is plunged through the skin. The plunge is made perpendicular to the skin so that the size of the puncture generally matches the size of the cutting blade.
An example of a lancet device that creates a plunge-type opening in the skin is shown in U.S. Pat. No. 4,203,446 to Hofert et al. entitled PRECISION SPRING LANCET. Hofert et al. discloses a spring lancet holder which employs means for minimizing the recoil transmitted to the lancet holder by the actuation of the drive mechanism which plunges the lancet into the skin. This is made possible by providing a mass which is caused to move in opposition to the motion of the lancet by a striker spring which is mounted between the lancet and the mass.
In U.S. Pat. No. 4,375,815 issued to Burns entitled RETRACTABLE LANCET ASSEMBLY discloses a lancet device which includes a coil spring positioned inside a housing for maintaining the lancet within the housing when the spring is in a substantially noncompressed state. The housing includes a plurality of elongated openings around its periphery each opening communicating through the side wall of the housing near the lancet. A slidable sleeve is positioned on the outside of the housing and includes a plurality of inwardly projecting feet which are in substantial alignment for projection through the openings in the housing. The feet are adapted to engage the lancet upon movement of the sleeve. This construction causes the spring to become noncompressed and thereby, automatically retracts the point of the lancet back inside the housing. In operation, this design allows the lancet to make a quickly penetrate the skin of the patient and in the same motion quickly retract back into the housing so that it does not dwell for any substantial length of time in the patients finger.
Another automatic retractable lancet assembly is disclosed in U.S. Pat. No. 4,388,925 issued to Burns entitled AUTOMATIC RETRACTABLE LANCET ASSEMBLY. This patent discloses an automatic retractable lancet assembly which comprises a housing with a sharp pointed lancet which is movably mounted therein. An actuating means moves the lancet outwardly from the housing and thereafter becomes disassociated from further movement of the lancet. Means are provided for automatically retracting the lancet back inside the housing.
In U.S. Pat. No. 4,442,836 issued to Meinecke et al. entitled BLOOD LANCET DEVICE discloses a blood lancet device which includes a housing with an exit opening for a lancet guide for guiding the puncturing and retraction of the lancet, a spring drive for the movement of the lancet, and a stop holding the lancet in the position remote from the part of the body from which the blood is to be taken. The exit opening for the lancet includes a release element which functions in connection with the stop.
In U.S. Pat. No. 4,624,253 issued to Burns entitled LANCET, and U.S. Pat. No. 4,677,979 also issued to Burns entitled LANCET a disposable lancet assembly is disclosed which includes integral strategically positioned abutments which serve dual functions. These functions include providing a snap action drive for the lancet and steps for lancet movement control. Also included are integral resilient means on the lance holder body providing a damping of the lancet device or the lancet drive in the puncture direction with automatic withdrawal of the lancet into the housing.
In the U.S. Pat. No. 4,869,249 issued to Crossman et al. a disposable lancet assembly is disclosed that includes a body and a lance with spring means acting between the lance and the body so that in the relaxed condition of the spring, the lance is in a first retracted position within the body. A cap for the body provides a passage through which the lance tip can move and a formation within the cap for engaging the lance in urging it into a second retracted position. Thus, the energizing means as the cap is fitted within body, engages a cap formation which enables the spring means to cause a momentary projection of the lance tip in the passage.
As can be seen, all of these lancets have blade motions which plunge the blade into the skin at an angle which is substantially perpendicular to the skin. It is desirable that the punctures created by these lancets be fairly deep so that good blood flow will result from the puncture. The reason for this is that plunge-type lancet devices typically utilize a pointed blade which creates a V-shaped incision into the patient. The widest region of the puncture is on the surface of the skin wall, the narrowest region coinciding with the point of the puncture. Since the narrowest portion is also the deepest point of the puncture a relatively deep puncture must be made to insure enough capillaries are severed to achieve the necessary bleeding. However, such deep punctures typically are very painful.
It is well known in the art that incisions made by scalpel slices are less painful than punctures made by plunging-type devices. Further, incisions are less intrusive and heal more readily than punctures. Additionally, punctures produced by devices which plunge into the skin subject the skin to forces which damages the skin tissue immediately surrounding the puncture. In contrast, devices which make scalpel like incisions require less downward force and thus, are less harmful to the surrounding skin tissue.
Devices that make scalpel like incisions are exemplified in U.S. Pat. No. 4,643,189 issued to Mintz entitled APPARATUS FOR IMPLEMENTING A STANDARDIZED SKIN INCISION. This device includes a housing having an internal hollow and a base containing an elongated slot. The internal hollow contains a movable pivot arm having a first pivotable end and a second end having a cam follower. There is a cam surface upon which the cam follower of the pivot arm rides. The pivot end of the arm includes a cutting edge which moves transversely while the arm is pivoting. The cam controls the path of the cutting edge as it enters the slot after the unit is triggered, the edge projecting through the slot in the housing along a given path to implement the incision. After traversing the path the cutting edge is withdrawn into the housing to prevent further use and injury.
Another lancet device which creates a scalpel like incision is disclosed in U.S. Pat. No. 5,212,879 entitled METHOD FOR MANUFACTURING A DISPOSABLE RETRACTABLE FIGURE STICK DEVICE, issued to Biro et al. and assigned to International Technidyne Corporation the assignee herein. This patent describes a finger stick device which includes a blade pivot arm having a first end pivotally coupled to a housing and a second end having a upper slope surface and a lower surface. A blade is affixed to the second end such that its cutting edge extends away from the lower surface. A resilient bias member when actuated, traverses the upper surface and depresses the second end of the blade pivot arm such that the blade exits the housing and incises the skin. The incising operation is complete upon the bias member traversing the sloped upper surface of the blade pivot arm.
Still another lancet device which makes a scalpel like incision is disclosed in U.S. Pat. No. 5,314,441 entitled DISPOSABLE LANCET ASSEMBLY, issued to Cusack et al. and assigned to International Technidyne Corporation the assignee herein. In this patent, a lancet device is described which uses a planar blade that implements an incision in the skin of the patient using a slicing action. The blade support arm is pivotally secured within a hollow housing. The pivot connection between the blade support arm and the housing is formed by a pivot pin which extends from the housing and is positioned in a slot receptacle formed on the blade support arm. The pivot pin is free to reciprocally move within the slot receptacle as the blade support arm pivots about the pivot pin. The rotation of the blade support arm about the pivot pin is implemented by a bias spring. The path traversed by the blade support arm as it pivots, is controlled by a groove located around the interior surface of the housing which engages a projection that extends from the blade support arm. Consequently, when the support arm pivots from a first position to a second position, the projection on the blade support arm traverses the groove in the housing, the action of the projection of the blade support arm following the groove in the housing causes the slot receptacle on the blade to reciprocate. This in turn causes the blade to reciprocate within the housing as it rotates with the blade support arm. The blade then exits the housing and implements an incision and is again retracted into the housing traversing a teardrop shaped path.
Although these incisional-type lancet devices have many advantages, a need still exists for easier operating devices which are cheaper to manufacture.
It is, therefore, an object of the present invention to provide an improved disposable self-activated lancet device that utilizes a blade mechanism which moves according to a molded and preset cam generated pattern which incises the finger.